This is undeniably true, but what does this have to do with water fasting? I took on this fast for the cleansing and healing benefits, and for spiritual reasons. To eliminate bad habits i had established and to start fresh with healthy/healthier eating habits. For me, the 7 or so "real" pounds of predominately fat i lost (of the 21 pounds total until the 14 pounds of water return) are merely a nice perk.
Perhaps you assume that everybody fasts only to lose weight?